The present invention relates generally to the field of substrate processing equipment. More particularly, the present invention relates to the detection of particles on a bevel of a semiconductor substrate. Merely by way of example, the method and apparatus of the present invention are used to detect particles in a photolithography coating system using a corona discharge technique. The method and apparatus can be applied to other processes for semiconductor substrates, for example those used in the formation of integrated circuits.
Modern integrated circuits contain millions of individual elements that are formed by patterning the materials, such as silicon, metal and/or dielectric layers, which make up the integrated circuit, to sizes that are small fractions of a micrometer. The technique used throughout the industry for forming such patterns is photolithography. A typical photolithography process sequence generally includes depositing one or more uniform photoresist (resist) layers on the surface of a substrate, drying and curing the deposited layers, patterning the substrate by exposing the photoresist layer to electromagnetic radiation that is suitable for modifying the exposed layer, and then developing the patterned photoresist layer.
It is common in the semiconductor industry for many of the steps associated with the photolithography process to be performed in a multi-chamber processing system (e.g., a cluster tool) that has the capability to sequentially process semiconductor wafers in a controlled manner. One example of a cluster tool that is used to deposit (i.e., coat) and develop a photoresist material is commonly referred to as a track lithography tool.
Track lithography tools typically include a mainframe that houses multiple chambers (which are sometimes referred to herein as stations) dedicated to performing the various tasks associated with pre- and post-lithography processing. There are typically both wet and dry processing chambers within track lithography tools. Wet chambers include coat and/or develop bowls, while dry chambers include thermal control units that house bake and/or chill plates. Track lithography tools also frequently include one or more pod/cassette mounting devices, such as an industry standard FOUP (front opening unified pod), to receive substrates from and return substrates to the clean room, multiple substrate transfer robots to transfer substrates between the various chambers/stations of the track tool, and an interface that allows the tool to be operatively coupled to a lithography exposure tool in order to transfer substrates into the exposure tool and receive substrates from the exposure tool after the substrates are processed within the exposure tool.
Over the years there has been a strong push within the semiconductor industry to shrink the size of semiconductor devices. As device size has decreased, the importance of reducing the presence of contaminant particles has increased since such particles may lead to the formation of defects during the semiconductor fabrication process. In order to maintain high manufacturing yield and low costs, the detection and removal of contaminant particles is desirable. Particles present on the wafer bevel may be dislodged and adhere to the front side of the wafer, potentially damaging integrated circuits formed on the front side of the wafer. Moreover, if particles present on the wafer bevel are dislodged and adhere to the backside of the wafer, non-planarity during lithography may result in lithographic depth of focus errors.
Some particle detection systems use optical detection methods that use a small laser spot to scan the backside of the substrate or wafer to detect light scattered off particles. However, these systems are not generally configured to detect particles present on the non-planar bevel of a substrate presents. Additionally, these particle detection systems do not provide the level of control desirable for bevel particle detection on current and future track lithography tools. Therefore, there is a need in the art for improved methods and apparatus for detecting particles on the backside of a semiconductor substrate in a track lithography tool.